The desirability of blanching vegetables, fruits, and other foodstuffs to prevent undesirable effects on quality during frozen, canned or dehydration storage has been recognized for many years. Although the effects of blanching may not be fully understood, it is generally recognized that blanching inactivates enzymes such as peroxidase and catalase which are naturally present in the foodstuffs. Inactivation of the enzymes prevents flavor degradation which may occur if the enzymes are present during storage.
Blanching typically involves bringing the vegetable or other foodstuff to an elevated temperature and holding it there for sufficient time to inactivate the enzymes. Blanching is also occasionally used to provide a precooking for vegetables which have relatively hard flesh such as rutabagas, carrots and others.
The prior art includes several different types of blanching apparatus used by the food processing industry. U.S. Pat. No. 2,403,871 to McBean discloses a relatively long blanching apparatus incorporating a retort tube which extends lengthwise down the machine. An endless conveyor apparatus having a number of pistons mounted at spaced positions along the conveyor extends through the retort tube. The pistons are properly sized to fit snugly within the retort tube and to convey units of food lengthwise down the retort tube. Food product is fed in between the pistons at one end of the retort tube and is conveyed therethrough by the movement of the pistons. Steam is introduced at a plurality of points along the retort tube to heat and create increased pressure therein. Food exits from the retort tube in a continuous flow after being blanched.
U.S. Pat. No. 4,092,911 to Goodale discloses a blanching apparatus using an elongated conveyor contained within a sealed enclosure. Entrance and exit portals are used to maintain a slightly elevated pressure within the sealed enclosure. The entrance and exit portals use rotating vanes which prevent direct flow of steam from the enclosure.
U.S. Pat. No. 4,238,997 to Hingstenberg shows an apparatus for blanching sauerkraut. The Hingstenberg apparatus uses a plurality of drums or other chambers which are rotatably mounted for partial contact with a hot water or water brine bath. The rotatable drums are arranged in series with the water bath increasing in temperature from the inlet to the exit. Sauerkraut or other food products are fed into the inlet and rotated within the perforated drums. Communicating passageways between adjacent drums causes the excess in an upstream drum to spill over into the next drum in the series, thereby providing a continuous flow of food product through the blancher.
Other prior art blanchers include those incorporating a continuous water bath through which vegetables are moved in order to properly blanch them. Also included in the prior art are hydrostatic steam blanching systems having water baths at each end and conveyors which transport the food products beneath the water surface and into a steam containing tunnel wherein the vegetables are blanched.
Prior art steam blanching systems suffer from a number of problems which continue to cause inefficiencies. A primary problem suffered by prior art steam and water bath blanching apparatus is the large amount of floor space necessary. This is particularly true with elongated tunnel steam blanchers or water bath type blanchers. The large amount of floor space consumed by these blanchers create substantial additional cost associated with new plant capital cost and maintenance cost.
Another problem associated with steam tunnel type blanchers is the substantial amounts of lost steam which escape from the apparatus. The escaped steam is significant for at least two reasons. Firstly, the escape of steam represents a loss of substantial amounts of energy which must be paid for in the production of steam. Many of the prior art steam blanchers process only one or two pounds of food product for each pound of steam consumed. This substantial amount of steam consumption adds to the price of the resulting food product and to the amount of investment in steam generating capacity necessary to support the food blanching line. Secondly, the escaped steam creates excessive humidity in the production facility which increases the amount of air which must be vented.
Production capacity prior art steam blanchers have also been limited in that they generally are not capable of developing significant pressurization inside so as to allow the blanching time to be significantly reduced. The savings in the amount of time necessary to blanch the product is needed to increase throughput and hence provide more economical operation. Increased steam pressure and operating temperatures also have been found advantageous in terms of the resulting product quality. Flavor, texture and color are all found to be improved with higher temperature and reduced time blanching.
Prior art food blanchers also suffer from problems of food residue buildup on exposed heated surfaces and on internal surfaces which may come into contact with the product being process. Strict sanitation requirements in food processing plants necessitate that any residue buildup be minimized so that bacteriological growth is minimized and product flavor and appearance is not degraded.
It is an object of this invention to provide a food product blanching and processing apparatus which easily and economically receives and pressure blanches or processes vegetables or other food products using pressurized steam.
It is an object of this invention to provide a blancher or food processor which is capable tumbling the food product during blanching so that uniform blanching occurs amongst all of the food product.
It is another object of this invention to provide a food blancher or processing unit which requires a minimum of steam consumption in order to blanch vegetables, fruits and other food products.
It is an object of the invention to provide a food blancher or processor which uses a minimum amount of floor space in a factory in which it is installed.
It is a further object of the invention to provide a food blancher or processor which eliminates drippage and food residue from accumulating on hot surfaces of the machine and which prevents any raw product from entering into the finished product.
It is a still further object of this invention to provide a method for rapidly and uniformly blanching food products in a minimum of time using pressurized steam.
These and other objects and advantages of the invention will be apparent from the description of the preferred embodiment of the invention given herein.